Conventionally, a high-speed liquid-filling machine equipped with a filling station illustrated in FIG. 9 for example, is known as a high-speed liquid-filling machine for filling liquid such as milk and juice to paper containers. Such a high-speed liquid-filling machine is equipped with: a machine frame 1 having a filling station; a transporting conveyor 2 capable of transporting containers in such a manner that they stop in succession at the filling station; a rotative body 4 having a radial mandrel 3, disposed upward of the starting end of the transport path of the transporting conveyor 2; a filling device 8 having a filling tank 5, a quantifying cylinder 6, and a filling nozzle 7, and a container lifting-and-lowering means 9, disposed at the filling station located in the midpoint of the transport path; a heat sealer 10 disposed on the latter half of the transport path, and so on.
Filling and packaging by the above high-speed liquid-filling machine is effected by the following steps of: unfolding a container material (carton blank) into a square-cylindrical shape, while taking it out from a magazine 11 retaining the container material which is capable of being formed into a square-cylindrical shape; inserting and setting the unfolded material in succession to the mandrel 3; heating the edged of the material that will form the bottom of the container by a bottom-heating device 12; folding flat the heated circumferential edge of the container by a container-edge folding device 13; crimping the above flat-folded edge by a container-bottom-application device 14 to form a square-cylindrical container with a bottom; and shifting the square-cylindrical container with a bottom from the mandrel to container holders fixed to endless chains 15. The above transporting conveyor 2 is comprised of: the endless chains 15 coupled with a plurality of the container holders; and a pair of sprockets 16 and 17 provided at the starting end and the terminal end of the transport path respectively, where the endless chains 15 are bridged.
The square-cylindrical containers with a bottom shifted onto the transporting conveyor are transported intermittently by the container holders fixed to the endless chains 15, over a rail 18 which provides a bottom support for and guides the containers. The square-cylindrical containers are then transported through a preparative folding device 19 which marks fold lines on the square-cylindrical containers with a bottom so that the top of the containers can be easily interfolded into a roof shape, and through a sterilizer 20 which sterilizes the inside of the container by oxygenated-water spray and/or ultraviolet irradiation, and finally reach the filling station. The square-cylindrical containers with a bottom intermittently transported and stopped at the filling station are then pushed up by the container lifting-and-lowering device 9. When the container reaches the top dead center, the filling nozzle 7 starts filling the descending container with liquid until the head of the filling nozzle 7 is withdrawn from the descended container, and the container-transporting starts almost at the same time as the filling is completed. The square-cylindrical containers with a bottom filled with liquid are then transported via a main-folding device 21 which finally interfolds the container top with the pre-folded lines into a roof shape, and via a container-top heating device 22 which heats the sealing surface of the interfolded container top. The container top is then heat-sealed by crimping by a heat sealer 10 and is printed with a date and the like by a printer 23, and then the containers are discharged as liquid-filled, packaged products.
Incidentally, chain conveyors used as container-transporting conveyors are commonly known to generate chain elongation due to abrasions of endless chains over a long period of use. For example, in roller endless chains, constituted by sequential combinations of pin links and roller links, wherein each pin link has pin link plates at both ends of the two pins, and each roller link has roller link plates at both ends of the two bushings on which the rollers are fitted rotatably, it is known that the pin and the bushing which respectively constitute slide portions are brought into contact with each other in use and hence, the pin and the bushing are abraded thus decreasing thickness thereof whereby the elongation of the endless chain is generated. The generated endless-chain elongations displace the center position of the container holders into the transporting direction resulting in various drawbacks such as the seizure of endless chain into a sprocket wheel or a conveyor rail at the time of transportation and the leaking of liquid from the container after filling besides the displacement of centering between the device such as the filling device operable in each group of devices and the container. Particularly, with respect to the displacement of centering, it has been absorbed by moving the filling device or the like in the conveying direction. However, there exists a limit with respect to the absorption of the displacement and hence, when the absorption of the displacement reached the limit, it has been determined that the lifetime of the endless chain had almost run down and the endless chains have been exchanged at the same time.
Meanwhile, as a technique for applying a preferred tension to the chains, a take-up of a chain conveyor is known, such take-up comprising: a holding arm which is freely pivotable within a given area where a driven sprocket bridged with chains is fixed at the head position and is so arranged that it can be moved closer to or further away from a drive sprocket; a biasing means biasing the holding arm into the direction to which the driven sprocket can be moved away from the drive sprocket; and a locking means which lock-releasably locks the pivot of the holding arm at any given position within the pivot area (see Japanese Laid-Open Patent Application No. 5-338758).
The latest type of this high-speed liquid-filling machine is made with a view to achieving an even higher performance (speeding up of the operation) without changing the number of rows and conveying pitches and hence, a time cycle of the intermittent operations of the conveyor is shortened. In order to conduct the given container supplying, filling, lid-material sealing and the like within this short time cycle, particularly within a short intermittent stop time, sections for container supplying, filling, lid-material sealing and the like are provided at plural sections. Providing plural sections for filling, sealing, sterilizing and the like inevitably leads to an elongated machine length. In the latest type of this filling-and-packaging machine with elongated machine length, in order to achieve higher performance, positioning accuracy of container holders transported to each station of container supplying, filling and lid-material sealing should be as precise as possible. However, as long as conventional endless chains are used in transporting conveyors, problems resulting from elongation of endless chains in use, more specifically, regular positioning adjustment of each station and replacement of endless chains for making as precise as possible the center-position accuracy of the container holders transported to each station for container supplying, filling and lid-material sealing, were simply unavoidable. Particularly, in conventional container transporting conveyor apparatuses, the drive source (drive sprocket) has to be provided at the downstream-side end of the transport path, and in this case, the displacement of the container holders due to chain elongation would arise more significantly as the distance from drive source of the transporting apparatus increases, namely, notably at the starting-end of the transport path. Hence, the container supplying device which is situated at the very starting-end side of the transport path is most susceptible to positioning displacement of container holders, which has been a serious problem. Moreover, another problem has been that, as stated above, as there is a limit to the chain-adjustment task, and chains that have elongated beyond this adjustment limit have to be replaced; and further that link parts are provided with some allowance which resulted in poor accuracy of stop position for the objects transported.